The invention relates to insulated fluid storage units, including hot water heaters.
Hot water heaters for domestic and other applications include an inner storage tank having an associated heating unit for heating water in the tank. In an electric hot water heater, the heating unit is typically an electric resistance heating coil within the tank. The tank is surrounded by suitable insulation to retain the heat and minimize the necessity for frequent reheating. An outer aesthetically pleasing jacket or shell is provided around the insulation.
The bottom of the tank and the bottom of the jacket are supported by a lower pan which typically includes thermally insulating base pad material to thermally insulate the tank from the pan and the support surface upon which the pan rests, such as a basement floor. In applications using expanded foam as the insulation between the tank and the outer jacket, the base pad also serves as a dam preventing leakage therepast of the resinous liquid applied to the annular space between the tank and the outer jacket, which resinous liquid foams and expands to produce a rigid and closely adhering insulating enclosure around the inner tank, and for which further reference may be had to U.S. Pat. Nos. 3,521,604 and 4,749,532.
Various types of base pads are known in the prior art. In one form, the base pad is a circular layer of fiberglass upon which the inner tank rests. The outer periphery of the fiberglass is in the annular space between the inner storage tank and the outer jacket, and provides the above noted dam in expanding foam applications.
It is also known in the prior art to provide a base pad precast to a specific size and shape and resting in a bottom pan and receiving the inner storage tank, for example as shown in U.S. Pat. No. 4,878,459, FIGS. 12 and 12a.
It is also known in the prior art, as shown in FIGS. 1 and 2 herein, to provide a base pad of expanded polystyrene material in the bottom pan and receiving the inner storage tank and the outer jacket.